Effect of boundary scattering on spin-hall effect

The spin dependent reflection in quasi-two-dimensional electron gas from an impenetrable barrier in presence of Rashba and Dresselhaus spin-orbit coupling is analyzed in detail. It is shown that due to spin-orbit effects the reflected beam split in two beams gives rise to multiple reflection analogous to phenomena birefringence. The interplay between Rashba and Dresselhaus spin-orbit coupling gives rise to anisotropy in Fermi energy surface and a non-zero net spin-polarized current oscillating with two frequencies for all the values of incident angle except at $45^{o}$ when averaged over all components of reflected beam. It is also shown that in over critical region, all the three polarization components as well as net polarization has non-zero values and are exponentially decaying as distance from the barrier increases which in turns spin-accumulation near the barrier is an important consequence of spin-hall effect.Comment: 6 pages, 8 figure

Reionization constraints on primordial magnetic fields

We study the impact of the extra density fluctuations induced by primordial magnetic fields on the reionization history in the redshift range: $6 < z < 10$. We perform a comprehensive MCMC physical analysis allowing the variation of parameters related to primordial magnetic fields (strength, $B_0$, and power-spectrum index $n_{\scriptscriptstyle \rm B}$), reionization, and $\Lambda$CDM cosmological model. We find that magnetic field strengths in the range: $B_0 \simeq 0.05{-}0.3$ nG (for nearly scale-free power spectra) can significantly alter the reionization history in the above redshift range and can relieve the tension between the WMAP and quasar absorption spectra data. Our analysis puts upper-limits on the magnetic field strength $B_0 < 0.358, 0.120, 0.059$ nG (95 % c.l.) for $n_{\scriptscriptstyle \rm B} = -2.95, -2.9, -2.85$, respectively. These represent the strongest magnetic field constraints among those available from other cosmological observables.Comment: Accepted for publication in MNRAS; 9 pages, 6 figure

Quasielastic electron- and neutrino-nucleus scattering in a continuum random phase approximation approach

We present a continuum random phase approximation approach to study electron- and neutrino-nucleus scattering cross sections, in the kinematic region where quasielastic scattering is the dominant process. We show the validity of the formalism by confronting inclusive ($e,e'$) cross sections with the available data. We calculate flux-folded cross sections for charged-current quasielastic antineutrino scattering off $^{12}$C and compare them with the MiniBooNE cross-section measurements. We pay special emphasis to the contribution of low-energy nuclear excitations in the signal of accelerator-based neutrino-oscillation experiments.Comment: 5 pages, 5 figures. Contribution to the proceedings of the 16th International Workshop on Neutrino Factories and Future Neutrino Beam Facilities (NUFACT-2014

Quasielastic contribution to antineutrino-nucleus scattering

We report on a calculation of cross sections for charged-current quasielastic antineutrino scattering off $^{12}$C in the energy range of interest for the MiniBooNE experiment. We adopt the impulse approximation (IA) and use the nonrelativistic continuum random phase approximation (CRPA) to model the nuclear dynamics. An effective nucleon-nucleon interaction of the Skyrme type is used. We compare our results with the recent MiniBooNE antineutrino cross-section data and confront them with alternate calculations. The CRPA predictions reproduce the gross features of the shape of the measured double-differential cross sections. The CRPA cross sections are typically larger than those of other reported IA calculations but tend to underestimate the magnitude of the MiniBooNE data. We observe that an enhancement of the nucleon axial mass in CRPA calculations is an effective way of improving on the description of the shape and magnitude of the double-differential cross sections. The rescaling of $M_{A}$ is illustrated to affect the shape of the double-differential cross sections differently than multinucleon effects beyond the IA.Comment: 10 pages, 10 figures. Version published in Physical Review